Add some missing FFI safe types #42
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These additional types have representations that are defined to be the same as some underlying FFI safe representation.
thomcc
reviewed
Jun 26, 2020
| compatible to a `*const T` and `*mut T` pointer; | ||
| - `core::num::NonZero*`, then is compatible to the corresponding integral | ||
| primitive type; | ||
| - a `repr(transparent)`-annotated `struct` with only one field, where that |
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You're allowed to have more than one field if one is a align-1 ZST. This is common for PhantomData, for example.
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You're even allowed to have an arbitrary amount of align-1 ZSTs, however this seemed very similar to the ZST restrictions below. The list style itself is not exactly exhaustive in either case. I have not yet seen any such use in ffi in the wild whereas I did find use for all other cases that I've listed.
polazarus
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Jun 27, 2020
danielhenrymantilla
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Jun 27, 2020
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Translation of pull request ANSSI-FR#42
polazarus
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Translation of pull request ANSSI-FR#42
polazarus
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Translation of pull request ANSSI-FR#42
polazarus
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polazarus
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Translation of pull request ANSSI-FR#42
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| - pointers, | ||
| - an `Option<T>` where `T` is either | ||
| - `core::ptr::NonNull<U>` and `U` is a `Sized` C-compatible type, then it is |
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The part with the pointers (such as *mut U) forget to express the U is a Sized ... invariant that Option<ptr::NonNull<U>> do.
I'd weaken the C-compatible bound on U, but explicit the Sizedrequirement:
Suggested change
| - pointers, | |
| - an `Option<T>` where `T` is either | |
| - `core::ptr::NonNull<U>` and `U` is a `Sized` C-compatible type, then it is | |
| - pointers to some type `Pointee`, where: | |
| - `Pointee : Sized`, | |
| - `Pointee` is either a C-compatible type too (and only then can the pointer be dereferenced by the C side), or it is not, in which case it must be treated as a pointer to an opaque object (_c.f._, the dedicated section \[FIXME:add link\]). | |
| - an `Option<T>` where `T` is either | |
| - `core::ptr::NonNull<Pointee>` where `Pointee` meets the constraints mentioned for the pointer case. |
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These additional types have representations that are defined to be the
same as some underlying FFI safe representation.